Patent Literature 1 describes an electronic device such as a mobile phone that transmits air conduction sound and bone conduction sound to the user. Also, Patent Literature 1 describes that air conduction sound is sound transmitted to the user's auditory nerve when vibration of the air, caused by vibration of an object, passes through the ear canal to the tympanic membrane, and the tympanic membrane vibrates. Patent Literature 1 further states that bone conduction sound is transmitted to the user's auditory nerve through a part of the user's body (e.g. the cartilage of external ear).
In the telephone described in Patent Literature 1, a rectangular flat plate vibrator made of piezoelectric bimorph and flexible substance is attached to the external surface of a housing through an elastic member. Also, Patent Literature 1 states that, when a voltage is applied to the piezoelectric bimorph of the vibrator, the piezoelectric material expands and contracts in the longitudinal direction, which causes the vibrator to vibrate, and when the user puts the vibrator to his/her auricle, air conduction sound and bone conduction sound are transmitted to the user.